The present invention relates to a key entry system which permits locking or unlocking of the door of a vehicle, unlocking of a steering lock, starting of an engine, and the like.
Such an "operation management system" as is disclosed in, e.g., Japanese Patent Application Unexamined Publication No. Hei. 7-150835 has already been known as an apparatus which locks or unlocks the door of a vehicle or starting of an engine in a non-contact manner without use of a mechanical key. FIG. 9 shows the configuration of the operation management system.
As shown in the drawing, the "operation management system" comprises a driver's license card 101 and a reading/checking section 105. The driver's license card 101 includes: an IC circuit 102 which is constituted by an ID memory for storing identifying data for identification purposes, a control section for controlling reading and writing of contents of the ID memory, a modulation circuit, a transmission circuit, and a rectifier supply circuit (any parts are not shown); and an antenna coil 103. The reading/checking section 105 is provided on the vehicle and is connected to an antenna 104. This reading/checking section 105 comprises an oscillation circuit 106 for transmitting data via the antenna 104, a receiving circuit 107 for receiving data via the antenna 104, a demodulator circuit 108 for demodulating a received signal, an ID memory 109, and a control circuit 110 which controls the reading and writing of contents of the ID memory 109. Upon receipt of an operation instruction from an ignition/push switch 111, the reading/checking section 105 is activated to send power to the driver's license card 101 by radio transmission, as well as to make a decision, on the basis of a return code signal received from the driver's license card 101, as to whether or not the driver is authorized to drive the vehicle.
In this case, when the driver's license card 101 is brought close to the antenna 104 provided in the vehicle, electromagnetic induction arises between the antenna coil 103 incorporated in the card and the antenna 104, so that power is supplied to the driver's license card. Further, code data are exchanged between the driver's license card and the reading/checking section, thereby enabling locking or unlocking of the door and the starting of an engine in a non-contact manner without using a mechanical key.
However, the foregoing existing "operation management system" suffers the following problem.
The communication range between the antenna coil 103 and the antenna 104 is considerably unsatisfactory in terms of the characteristics of the currently-used RKE (Remote Key Entry) function. Particularly, in a case where the antenna 104 is provided on the vehicle, a considerably amount of leakage magnetic flux arises, because the vehicle body is made of a magnetic substance. As a result, data communications can be carried out only within a short distance of 10 cm or less.
Since the driver's license card 101 must be brought in parallel with the antenna 104 provided on the vehicle, there is a limit to the angle at which the driver's license card 101 is held to the antenna 104, imposing an inconvenience on the user.
As mentioned above, in spite of the fact that the portability of the key is improved by forming the key in the form of a card, since transmission and receipt of data are carried out only through electromagnetic induction, the user cannot lock or unlock a door lock while holding the driver's license card 101 in a pocket or wallet.